Finishing machine including pressure responsive valve peripherally sealing tub drain openings

ABSTRACT

A finishing machine is provided with a pressure responsive valve adapted to peripherally seal a plurality of closely spaced drain openings formed through the lower wall of the vibratory tub. A generally circular diaphragm is clamped between a base plate and an annular clamping plate. The base plate is apertured to admit the discharge pressurized fluid to and from the chamber defined between the diaphragm and the base plate. The diaphragm includes a circular closure portion surrounded by a thinner annular expansible portion. When pressurized fluid is admitted to the chamber the closure portion retains its substantially planar configuration while the expansible portion expands to move the closure portion into peripheral sealing engagement with the region of the openings.

United States Patent 1 Rampe Nov. 6, 1973 [75] Inventor: John F. Rampe, Cleveland, Ohio [73] Assignee: Rampe Research, Cleveland, Ohio [22] Filed: June 29, 1971 [21] Appl. No.: 158,042

[52] US. Cl. 51/163, 251/61.1 [51] Int. Cl B24b 31/06 [58] Field of Search 51/163;251/61.1

[56] References Cited UNITED STATES PATENTS 3,191,348 6/1965 Rampe 51/163 2,545,944 3/1951 2,705,608 4/1955 2,715,418 8/1955 2,705,595 4/1955 Carlson 251/61.1 X

Primary Examiner-Harold D. Whitehead AttameyWatts, Hoffmann et al.

[57] ABSTRACT A finishing machine is provided with a pressure responsive valve adapted to peripherally seal a plurality of closely spaced drain openings formed through the lower wall of the vibratory tub. A generally circular diaphragm is clamped between a base plate and an annular clamping plate. The base plate is apertured to admit the discharge pressurized fluid to and from the chamber defined between the diaphragm and the base plate. The diaphragm includes a circular closure portion surrounded by a thinner annular expansible portion. When pressurized fluid is admitted to the chamber the closure portion retains its substantially planar configuration while the expansible portion expands to move the closure portion into peripheral sealing engagement with the region of the openings.

24 Claims, 6 Drawing Figures PATENTEDHHY 6|973 3769.759 SHEET 1m 2 INVENTOR. JOH N F. RA MP E ATTORNEYS slvssl'rss PATENTEI] IIIIV 6 I973 SHEET 2 BF 2 INVENTOR. JOHN F: RAMPB WWI ATTORNEYS FINISHING MACHINE INCLUDING PRESSURE RESPONSIVE VALVE PERIPHERALLY SEALING TUB DRAIN OPENINGS CROSS-REFERENCE TO RELATED PATENT Vibratory Finishing Machine, U.S. Pat. No. 3,449,869 issued June 17, 1969 to J. F. Rampe.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to vibratory finishing machines and more particularly to a pressure responsive valve for peripherally sealing a plurality of closely spaced drain openings formed through the lower wall of the vibratory tub.

2. Prior Art Vibratory finishing machines commonly employ a tub which is movably supported above a base. A vibratory drive system is adapted to vibrate the tub within the range of approximately 900 to 1,800 cycles per minute. While the finishing machine tub is ordinarily provided with an exit door through which the abrasive media and finished work-pieces are extracted, it frequently becomes necessary to flush residue from the tub of the finishing machine at the end of the finishing operation. For this purpose, a numberof small, closely spaced drain openings are provided in the bottom of the finishing machine tub and a valve is required to close these openings.

in the past, hand operated valves have been employed for this purpose. Such hand operated valves have the advantage that they may be simply constructed to provide a member which may be rigidly clamped against the tub to minimize vibratory wear. However, such manual valves have disadvantages of being difi'icult to reach and awkward to operate. Moreover, such valves commonly have the disadvantage of providing an imperfect seal if abrasive. residue or other foreign matter becomes lodged or deposited adjacent the drain openings.

Remotely operated pressure responsive valves employing an expansible diaphragm are well known. Such known valves commonly employ a diaphragm which is uniformly pliable and extensible. The diaphragm is ordinaril'yv used to selectively open and close a single opening.

Most prior art pressure responsive valves are not suitable for use in sealing drain openings in the tub of a vibratory finishing machine. This is true for a number of reasons. First, where such pressure responsive valves employ diaphragms, most such diaphragms are relatively thin and uniformly pliable. Such flexibility results in the diaphragms partially entering the openings they seal. This renders the diaphragms subject to excessive wear due to vibration during operation of the finishing machine.

Second, where prior art pressure responsive valves employ diaphragms of sufficient thickness to prevent the diaphragmsvfrom entering the openings they seal, most such diaphragms provide an imperfect seal in the presence of abrasive residue adjacent the drain openings. It must be realized that both particles of abrasive compound and work piece grindings are flushed through the tub drain openings. Such particles occasionally lodge or deposit adjacent the drain openings. Nonetheless, an effective closure of the drain openings must be made.

Third, the diaphragms of most prior art valves are not sufficiently abrasion and wear resistant to repeatedly provide an effective seal in the presence of abrasive particles without undue wear and without deteriorating due to corrosion. Since valves sealing the tub of a vibratory finishing machine must occasionally close against abrasive particles, the diaphragms must necessarily be constructed so as to withstand abrasion and wear.

SUMMARY OF THE INVENTION The present invention overcomes the foregoing disadvantages of the prior art and provides a finishing machine with an improved pressure responsive valve including a diaphragm of novel configuration adapted to peripherally seal a plurality of closely spaced openings.

in accordance with one aspect of the present invention, the diaphragm is provided with a centrally disposed circular closure portion having a diameter which is greater than the maximum diameter of the region of the openings to be sealed. The diaphragm is thereby adapted to entirely surround the region of the openings to provide an effective peripheral seal. By the provision of such a peripheral seal, it is not necessary to seal the region between each of the openings. Hence, if particles of abrasive residue become lodged adjacent the openings, the closure portion may deflect in this region to accommodate the abrasive residue thereby permitting communication between the openings but still providing an effective peripheral seal which seals the entire region around the openings.

r The novel diaphragm structure additionally includes an annular expansible region formed integrally with and surrounding the periphery of the closure portion. The expansible portion comprises a thickness which is less than the thickness of the closure portion. By this arrangement, the closure portion is adapted to retain its substantially planar configuration while the expansible portion extends and contracts to move the closure portion into and out of engagement withthe openings. Hence the thicker closure portion serves to seal the drain openings without entering the openings themselves. This substantially'increases the operation life of the'diaphragm.

An annular clamping portion is disposed outwardly from the expansible portion and fis formed integrally therewith. An annular clamping means is provided to clamp the clamping portion to a base plate to provide a fluid-tight seal. A chamber is defined between the base plate and the diaphragm. Th'ebase plate is apertured to admit and release pressurized fluid from the chamber to expand and contract the ciaphragm. By this arrangement an extremely simple valve structure is provided which is easily installed and replaced beneath the tub of a vibratory finishing machine. Moreover, valves constructed in accordance with the the present invention are sufficiently inexpensive that a plurality of them may be employed to respectively close a similar number of regions each containing a plurality of closely spaced openingsr'lhe valve chambers are then interconnected for concurrent actuation.

In accordance with still another aspect of the present invention, the valve diaphragm is formed of a relatively stiff polyurethane material which is corrosion and abrasion resistant to assure a long operating life.

Accordingly, it is the principal object of the present invention to provide a finishing machine with an effective and durable pressure responsive valve adapted to peripherally seal a plurality of closely spaced openings formed through the lower wall of the vibratory tub of the machine.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a vibratory finishing machine including a plurality of pressure responsive valves constructed in accordance with the present invention mounted beneath the finishing machine tub;

FIG. 2 is an end elevational view of the machine of FIG. 1;

FIG. 3 is a top plan view of the valve of the present invention, as seen from the plane indicated by the line 3-3 in FIG. 4;

FIG. 4 is a cross-sectional view of the valve of the present invention as seen from the plane indicated by the line 4-4 in FIG. 3 and shown in conjunction with a portion of the vibratory finishing machine tub, the valve being shown in the open position;

FIG. 5 is a cross-sectional view similar to FIG. 4 with the valve shown in the closed position providing'a peripheral seal about the region of the openings; and

FIG. 6 is an enlarged top plan view illustrating a portion of the finishing machine tub having a plurality of closely spaced openings and showing the region of the peripheral seal which is provided by the valve of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a vibratory finishing machine is shown generally at 10. The finishing machine 10 includes an upstanding base support structure 11. A receptacle or tub 12 is movably supported above the base 11. A vibratory drive, indicated generally by the numeral 13, is connected to the tub 12 for cylically vibrating the tub typically at rates of from 900 to 1,800 cycles per minute. A vibratory finishing machine of this type is described and shown in the referenced Rampe patent.

In operation, workpieces such as castings, which are to be deburred, burnished, descaled or cleaned are deposited in the open top tub 12 with a supply of suitable abrasive media. The tub is then vibrated to perform the required finishing operation. When the finishing operation is completed, the finished workpieces and the abrasive media are discharged from the tub 12 through a door 14, shown in FIG. 2.

A plurality of pressure responsive valves 20 are provided to facilitate the cleaning of the tub 12. As will be explained in greater detail, each of the valves 20 serves to close a region of the lower tub wall which has a plurality of closely spaced discharge openings. When the valves 20 are opened, water may be introduced into the tub 12 to flush residue from the tub through the openings and into a catch-trough 15 formed beneath the tub 12. When the valves are closed, the openings are sealed to prevent the escape of fluid during finishing operations.

In order to control the valves 20, a series of pressure hoses 21 connect the valves to a control mechanism 22. The control mechanism 22 is provided with an actuator 23 which is selectively movable between closed and open positions. When the actuator 23 is in the closed position, the control mechanism serves to connect the valves 20 through a supply conduit 24 to a source of pressurized fluid 25. The valves 20 close when pressurized fluid is admitted to their chambers. When the actuator 23 is in the open position, the pressure hoses 21 are vented to atmosphere to release the pressurized fluid and open the valves. In the preferred embodiment, the pressurized fluid used to operate the valves 20, comprises compressed air.

Referring to FIG. 3, each of the valves 20 includes a base plate 30. An annular clamping plate 31 is provided with a central opening 32. The radially inwardly facing edges of the clamping plate which define the opening 32 are rounded to prevent their cutting into the diaphragm during operation of the valve 20. A diaphragm indicated generally by the numeral 33 includes an annular clamping portion 34 which is sandwiched between the clamping plate 31 and the base plate 32. A plurality of .threaded fasteners 35 extend through aligned openings formed in the base plate 30 and the clamping plate 31 to clamp the diaphragm 33 against the base plate 30 to provide a fluid-tight seal therebetween Referring to FIG. 4, it may be seen that the valve 20 is supported beneath the lower wall. of the tub 12 opposite a region 40 which has a plurality of closely spaced openings 41. A pair of mounting brackets 42 are welded to the underside of the lower wall of the tub 12. Threaded apertures 43 are provided through the brackets 42. Threaded fasteners in the form of high strength cap screws 44 are threaded into the apertures 43.

The base plate 30 has through mounting holes 45. The capscrews 44 extend through mounting holes 45. A pair of threaded nuts 46 are threaded onto each of the capscrews 44. The nuts 46 engage opposite sides of the base plate 30 to hold it in position. By this arrangement, the base plate 30 is adjustably positioned relative to the bottom wall of the tub 12.

As was previously mentioned, the diaphragm 33 includes an annular clamping portion 34. A depending annular bead 48 is formed integrally with the clamping portion '34 to' facilitate the formation of a fluid-tight seal between the diaphragm 33 and the base plate 30. The diaphragm 33 additionally includes a circular, centrally disposed closure portion 50. An annular expansible portion indicated generally by the numeral 51 is formed integrally with the periphery of the, circular closure portion 50 and with the annular calmping portion 34. The expansible portion 51 comprises a first annular portion 52 extending radially inwardly from the annular clamping portion 34, and a second annular portion 53 extending through the opening 32 to connect with the periphery of the closure portion 50. By this arrangement, the expansible portion 51 is of substantially L-shaped cross section and, as illustrated in FIG. 5, tends to straighten out during expansion.

The diaphragm 33 preferably comprises an abrasion resistent, corrosion resistent, resilient material such as polyurethane. The closure portion 50 is formed of a thickness greater than the thickness of the expansible portion 51. By this arrangement, the closure portion tends to retain a substantially planar configuration while the expansible portion may expand and contract to move the closure portion toward and away from the mounting plate 30. Y

A number of advantages of the novel diaphragm structure of the present invention are illustrated in FIG. 5. First, as will be apparent, the closure portion 50 is sufficiently rigid to prevent its deflection into any of the openings 41. Hence, during vibratory operation of the tub 12, the closure portion is not subject to a wearing action caused by transverse movement of the diaphragm relative to the openings 41. Second, the closure portion is sufficiently flexible topermit its deflection around a particle of abrasive residue 60 deposited between the openings 41. Third, while the diaphragm may deflect to permit communication between the openings 41, am effective peripheral seal is nonetheless maintained around the region 40 of the openings 41.

Referring to FIG. 6, the array of openings 41 is shown as being disposed within a substantially circular region of diameter D,. The peripheral seal provided by the diaphragm 33 is spaced from the region of the openings 41 and has a diameter D,. As will be apparent, the peripheral seal provided by the diaphragm 33 is sufficiently spaced about the region of the openings 41 to provide an effective seal despite the deposit of abrasive residue adjacent the openings 41.

Returning to FIG. 4, it may be seen that a chamber 61 is defined between the diaphragm 33 and the base plate 30. The base plate is provided with an aperture 62 extending therethrough. A threaded coupling 63 is welded to the underside of the base plate 30 in alignment with the aperture 62. The pressure hose 21 is provided with a threaded connector 64 which is'threaded into the coupling 63 to provide a fluid-tight connection. By this arrangement, pressurized fluid from the hose 21 may be admitted to and discharged from the chamber 61 through the opening 62.

During normal operation of the finishing machine, the actuator 23 of the control mechanism 22 is positioned in the closed position whereby pressurized fluid is admitted to the valve chambers 61 to close the valves 20. When, however, it is desired to clean the tub 12, the actuator 23 is moved to the open position thereby releasing pressurized fluid from the valve chambers 61 and permitting ;the valves to open. Water or other cleaning fluid may then be admitted to the tub 12 to flush the tub clean of abrasive residue.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood thatthe present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is: I

1. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a valve adapted to close a plu rality of closely spaced openings formed through the lower wall of the receptacle, comprising:

a. a base plate adapted to be positioned substantially adjacent the wall at a position opposite the openmgs;

b. a diaphragm having a centrally disposed closure portion, an expansible portion of substantially uniform width connecting with the periphery of said closure portion, and a clamping portion connecting with the periphery of said expansible portion;

c. clamping means engaging said clamping portion to clamp said clamping portion to said base plate to form a fluid-tight seal therebetween;

(1. said diaphragm and said base plate defining a chamber therebetween;

e. an aperture formed through said base plate for selectively admitting and releasing a pressurized fluid to and from said chamber;

f. said expansible portion being more flexible than said closure portion whereby said closure portion retains a substantially planar configuration while said expansible portion expands and contracts to move said closure portion when pressurized fluid is admitted to and discharged from said chamber; and, I

g. said closure portion being adapted to effect a peripheral seal with the lower receptacle wall around an area which is larger than the region of the spacedopenings, which area includes the region of said spaced openings, and, in the absence of foreign matter deposits around the individual openings, to effect a seal around each of said openings.

2. The machine of claim 1 wherein said closure portion is substantially circular and said expansible portion is substantially annular, said closure portion having a diameter which is greater than the maximum diameter of the region of the spaced openings.

3. The machine of claim- Zwherein said closure portion and said clamping portion are each substantially planar and extend within substantially parallel planes.

4. The machine of claim 3 wherein said expansible portion comprises a first annular portion extending radially inwardly from said clamping portion substantially in the plane of said clamping portion, and a second annular portion connecting said first annular portion and said closure portion, whereby said expansible portion comprises a substantially L-shaped cross section which tends to straighten out during expansion to move said closure portion toward the region of the spaced openings. I I

5. The machine of claim 4 wherein said clamping means comprises an annular clamping plate having a central opening and means to clamp said clamping plate to said base plate with said clamping portion sandwiched therebetween.

6. The machine of claim 5 wherein said first annular portion extends substantially radially inwardly from said annular clamping plate and said second annular portion extends through said central opening in said clamping plate whereby said clamping portion is disposed on one side of said clamping plate and said closure portion is disposed on the other side of said clamping plate. 1

7. The machine of claim 6 wherein:

a. the periphery of said clamping plate is substantially circular and has a diameter greater than the periphery of said diaphragm;

- b. said clamping plate and said base plate have aligned openings formed 'therethrough readially outwardly of said periphery of said diaphragm; and,

c. said clamping means comprises'threaded fastening means extending through said aligned openings.

8. The machine of claim7 wherein said clamping portion additionally includes anannular bead formed integrally wherewith to facilitate the formation of a fluid-tight seal between said diaphragm and said base plate.

9. The machine of claim 8 wherein the radially inwardly facing edges of said clamping'plate are rounded to prevent their cutting into said expansible portion.

10. The machine of claim 9 wherein said base plate includes mounting portions formed integrally therewith which extend radially outwardly beyond the outer diameter of said clamping plate.

11. The machine of claim 8 wherein said diaphragm comprises polyurethane.

12. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a pressure responsive valve adapted to close a plurality of closely spaced openings formed through the lower wall of the receptacle, comprising:

a. a base plate adapted to be positioned and substantially adjacent the wall at a position opposite the openings;

b. a generally circular diaphragm having a centrally disposed circular closure portion,'and annular expansible portion of uniform width formed integrally with the periphery of said closure portion, and a clamping portion formed integrally with the periphery of said expansible portion;

c. annular clamping means engaging said clamping portion to clamp said clamping portion to said base plate to form a fluid-tight seal therebetween;

d. an aperture formed through said base plate for selectively admitting and releasing a pressurized fluid to and from said chamber;

e. said'closure portion comprising a material of a thickness greater than the thickness of said expansible portion whereby said closure portion is adapted to retain a substantially planar configuration while sa id expansible portion may expand and contract to move said closure. portion 'when'pressurized fluid is admitted to and discharged from said chamber; and, r

iv. said diaphragm being adapted to engage the lowe wall in the region'of the openings to seal such ones of the openings as do not have deposits of foreign materials therearound, and to effect a peripheral seal around the region of said openings.

13. The machine of claim 12 wherein said closure portion and said clamping portionare eachsubstantially planar and extend within substantially parallel planes. I

14. The machine of claim 13 wherein said expansible portion comprises a first annular portion extending radially inwardly from said clamping portion substantially in the plane of said clamping portion, and a second an- 'nular portion connecting said first annular portion and said closure portion, whereby said expansible portion comprises a substantially L-shaped cross section which tends to straighten out during expansion to movesaid closure portiontoward the region of the openings.

a. the periphery of said clamping plate is substantially circular and has a diameter greater than the periphery of said diaphragm;

b. said clamping .plate and said base plate have aligned openings formed therethrough radially inwardly of said periphery of said diaphragm; and,

c. said clamping means comprises threaded fastening means extending through said aligned openings.

17'. The machine of claim 16 wherein said expansible portion extends substantially radially inwardly of said annular clamping plate and through said central opening whereby said clamping portion is disposed beneath said clamping plate and said closure portion is disposed above said clamping plate.

18. The machine of claim 17 wherein said clamping portion additionally includes an annular bead formed integrally therewith to facilitate the formation of a fluid-tight seal between said clamping portion and said base plate.

19. The machine of claim 18 wherein the radially inwardly facing edges of said clamping plate are rounded to prevent their cutting into said expansible portion.

20. The machine of claim 19 wherein said base plate includes mounting portio s formed integrally therewith which extend radially outwardly beyond the outer diameter of said clamping plate.

21. The machine of claim 18 wherein said diaphragm comprises polyurethane.

22. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a receptacle drainage system for selectively draining liquids from or retaining liquids within the receptacle, comprising:

a. a plurality of closely spaced drain openings formed in the lower wall of the receptacle;

b. a pressure responsive valve for closing said drain openings including:

i. a diaphragm having portions movable toward and away from the lower wall of the receptacle;

ii. mounting means positioning said diaphragm near said drain openings;

iii. said mounting means and said diaphragm defining'a chamber therebetween which, when filled with a pressurized fluid, will'effect movement of said diaphragm portions toward the lower wall;

iv. said diaphragm being adapted to engage the lower wall in the region of the openings to seal such ones of the openings as do not have deposits of foreign materials therearound, and to effect a peripheral seal around the region of said openrngs. I

23. The apparatus of claim 22 wherein:

a. said diaphragm is of generally circular shape having a centrally disposed circular closure portion, an annular expansible portion of uniform width extending around and formed integrally with the periphery of said closure portion, and a clamping portion extending around and formed integrally with the periphery of said expansible portion;

b. said mounting means includes clamping means engaging said clamping portion; and,

c. said closure portion is movable toward and away from the lower wall to selectively seal said openrngs. I

pand and contract to move said closure portion as pressurized fluid is admitted to and discharged from said chamber. 

1. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a valve adapted to close a plurality of closely spaced openings formed through the lower wall of the receptacle, comprising: a. a base plate adapted to be positioned substantially adjacent the wall at a position opposite the openings; b. a diaphragm having a centrally disposed closure portion, an expansible portion of substantially uniform width connecting with the periphery of said closure portion, and a clamping portion connecting with the periphery of said expansible portion; c. clamping means engaging said clamping portion to clamp said clamping portion to said base plate to form a fluid-tight seal therebetween; d. said diaphragm and said base plate defining a chamber therebetween; e. an aperture formed through said base plate for selectively admitting and releasing a pressurized fluid to and from said chamber; f. said expansible portion being more flexible than said closure portion whereby said closure portion retains a substantially planar configuration while said expansible portion expands and contracts to move said closure portion when pressurized fluid is admitted to and discharged from said chamber; and, g. said closure portion being adapted to effect a peripheral seal with the lower receptacle wall around an area which is larger than the region of the spaced openings, which area includes the region of said spaced openings, and, in the absence of foreign matter deposits around the individual openings, to effect a seal around each of said openings.
 2. The machine of claim 1 wherein said closure portion is substantially circular and said expansible portion is substantially annular, said closure portion having a diameter which is greater than the maximum diameter of the region of the spaced openings.
 3. The machine of claim 2 wherein said closure portion and said clamping portion are each substantially planar and extend within substantially parallel planes.
 4. The machine of claim 3 wherein said expansible portion comprises a first annular portion extending radially inwardly from said clamping portion substantially in the plane of said clamping portion, and a second annular portion connecting said first annular portion and said closure portion, whereby said expansible portion comprises a substantially L-shaped cross section which tends to straighten out during expansion to move said closure portion toward the region of the spaced openings.
 5. The machine of claim 4 wherein said clamping means compRises an annular clamping plate having a central opening and means to clamp said clamping plate to said base plate with said clamping portion sandwiched therebetween.
 6. The machine of claim 5 wherein said first annular portion extends substantially radially inwardly from said annular clamping plate and said second annular portion extends through said central opening in said clamping plate whereby said clamping portion is disposed on one side of said clamping plate and said closure portion is disposed on the other side of said clamping plate.
 7. The machine of claim 6 wherein: a. the periphery of said clamping plate is substantially circular and has a diameter greater than the periphery of said diaphragm; b. said clamping plate and said base plate have aligned openings formed therethrough readially outwardly of said periphery of said diaphragm; and, c. said clamping means comprises threaded fastening means extending through said aligned openings.
 8. The machine of claim 7 wherein said clamping portion additionally includes an annular bead formed integrally wherewith to facilitate the formation of a fluid-tight seal between said diaphragm and said base plate.
 9. The machine of claim 8 wherein the radially inwardly facing edges of said clamping plate are rounded to prevent their cutting into said expansible portion.
 10. The machine of claim 9 wherein said base plate includes mounting portions formed integrally therewith which extend radially outwardly beyond the outer diameter of said clamping plate.
 11. The machine of claim 8 wherein said diaphragm comprises polyurethane.
 12. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a pressure responsive valve adapted to close a plurality of closely spaced openings formed through the lower wall of the receptacle, comprising: a. a base plate adapted to be positioned and substantially adjacent the wall at a position opposite the openings; b. a generally circular diaphragm having a centrally disposed circular closure portion, and annular expansible portion of uniform width formed integrally with the periphery of said closure portion, and a clamping portion formed integrally with the periphery of said expansible portion; c. annular clamping means engaging said clamping portion to clamp said clamping portion to said base plate to form a fluid-tight seal therebetween; d. an aperture formed through said base plate for selectively admitting and releasing a pressurized fluid to and from said chamber; e. said closure portion comprising a material of a thickness greater than the thickness of said expansible portion whereby said closure portion is adapted to retain a substantially planar configuration while said expansible portion may expand and contract to move said closure portion when pressurized fluid is admitted to and discharged from said chamber; and, iv. said diaphragm being adapted to engage the lower wall in the region of the openings to seal such ones of the openings as do not have deposits of foreign materials therearound, and to effect a peripheral seal around the region of said openings.
 13. The machine of claim 12 wherein said closure portion and said clamping portion are each substantially planar and extend within substantially parallel planes.
 14. The machine of claim 13 wherein said expansible portion comprises a first annular portion extending radially inwardly from said clamping portion substantially in the plane of said clamping portion, and a second annular portion connecting said first annular portion and said closure portion, whereby said expansible portion comprises a substantially L-shaped cross section which tends to straighten out during expansion to move said closure portion toward the region of the openings.
 15. The machine of claim 14 wherein said clamping means comprises an annular clamping plate having a central opening, and means to clamp said clamping plate to said base plate with said clamping portion sandwiched therebetween.
 16. The machine of claim 15 wherein: a. the periphery of said clamping plate is substantially circular and has a diameter greater than the periphery of said diaphragm; b. said clamping plate and said base plate have aligned openings formed therethrough radially inwardly of said periphery of said diaphragm; and, c. said clamping means comprises threaded fastening means extending through said aligned openings.
 17. The machine of claim 16 wherein said expansible portion extends substantially radially inwardly of said annular clamping plate and through said central opening whereby said clamping portion is disposed beneath said clamping plate and said closure portion is disposed above said clamping plate.
 18. The machine of claim 17 wherein said clamping portion additionally includes an annular bead formed integrally therewith to facilitate the formation of a fluid-tight seal between said clamping portion and said base plate.
 19. The machine of claim 18 wherein the radially inwardly facing edges of said clamping plate are rounded to prevent their cutting into said expansible portion.
 20. The machine of claim 19 wherein said base plate includes mounting portions formed integrally therewith which extend radially outwardly beyond the outer diameter of said clamping plate.
 21. The machine of claim 18 wherein said diaphragm comprises polyurethane.
 22. In a finishing machine of the type including a supporting structure and a receptacle movably carried by the supporting structure and adapted to impart a finishing action to workpieces positioned within the receptacle, the improvement of a receptacle drainage system for selectively draining liquids from or retaining liquids within the receptacle, comprising: a. a plurality of closely spaced drain openings formed in the lower wall of the receptacle; b. a pressure responsive valve for closing said drain openings including: i. a diaphragm having portions movable toward and away from the lower wall of the receptacle; ii. mounting means positioning said diaphragm near said drain openings; iii. said mounting means and said diaphragm defining a chamber therebetween which, when filled with a pressurized fluid, will effect movement of said diaphragm portions toward the lower wall; iv. said diaphragm being adapted to engage the lower wall in the region of the openings to seal such ones of the openings as do not have deposits of foreign materials therearound, and to effect a peripheral seal around the region of said openings.
 23. The apparatus of claim 22 wherein: a. said diaphragm is of generally circular shape having a centrally disposed circular closure portion, an annular expansible portion of uniform width extending around and formed integrally with the periphery of said closure portion, and a clamping portion extending around and formed integrally with the periphery of said expansible portion; b. said mounting means includes clamping means engaging said clamping portion; and, c. said closure portion is movable toward and away from the lower wall to selectively seal said openings.
 24. The apparatus of claim 23 wherein said closure portion comprises a material of a thickness greater than the thickness of said expansible portion, and said closure portion is adapted to retain a substantially planar configuration while said expansible portion may expand and contract to move said closure portion as pressurized fluid is admitted to and discharged from said chamber. 